You know about the info_notnull explosion hack. You know about making monsters drop weapons or alternate ammo using the .weapon and .ammo_whatever hacks. You know about making items float in the air by spawning them on a temporary platform. Let's have a thread where we talk about new ways to use existing behavior and get novel gameplay. If you're a "retired" mapper, this is a great time to do some armchair level design and suggest ideas you'll never have a chance to use yourself.

Here's one i thought of a while ago. You all know that only the first 4 info_intermissions can get used in a level. You could set it up so that if a player meets some requirements (like finding some special secret, killing all the monsters, or something) you killtarget all 4 "regular" info_intermissions, so that the 5th one gets used instead -- and the 5th one would point to some cool secret vista.

Ok, just figured this one out, it follows on from the stuff I posted in the mapping help thread, but that isn't required reading to understand how to do it. Take any item that respawns in deathmatch(I've only tested ammo but see no reason why anything else should fail). Give it the following fields
targetname shells01
target shells01respawn
use SUB_regen

Then make a trigger relay with these fields
targetname shells01respawn
target shells01respawn
delay 20

Here's the flow of action. You pick up the shells(or whatever) and so the shells fires it's target. The target is the trigger relay, which begins counting to 20. When it reaches 20, it fires it's target, which is back to the shells. Here's the cunning hack, the use function of the shells is SUB_regen, the function called in dm to respawn items. So the shells are respawned! If you have multiple items you'll get odd behaviour if you don't give them all unique names.

Of course, you aren't constrained to items respawning on a timer. You could have an arena with items, two waves of monsters, and then have all the items respawn once the second wave comes in. Assuming killing all the monsters sets off a trigger_counter with target "secondwave", give the items you want respawned the following keys:
use SUB_regen
targetname secondwave

Et voila! Loads more ammo just in time for the next attack. And for once you're probably saving entities, handy for those maps which are pushing the limits in that direction. Luckily calling SUB_regen is perfectly safe on items that are already spawned. You get the respawn noise even if it's already there, but the item isn't affected at all.

Ok, I think that's enough for tonight. Tomorrow I might do a few reposts, the triggerable trigger and the heal trigger and those, along with further experiments into unusual ammo supplies and perhaps something very old and special...